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Cryptography

Types of Attacks

  • Cryptanalysis: Attacker tries to crack the cipher by exploiting weaknesses in the algorithm or implementation.
  • Brute Force: Attacker tries every possible key combination until the correct one is found.

Types of Encryption

  • Symmetric: Same key is used for encryption and decryption.
    • Examples: DES, AES
  • Asymmetric: Different keys are used for encryption and decryption.
    • Example: RSA

Block vs Stream Cipher

  • Block Cipher: Data is divided into fixed-size blocks and each block is encrypted/decrypted separately.
    • Examples: DES, AES
  • Stream Cipher: Data is encrypted/decrypted one byte or bit at a time.

DES (Data Encryption Standard)

  • Symmetric block cipher
  • 64-bit block size
  • 56-bit key size (relatively short and insecure over time)
  • Triple DES: Improved variant that applies DES three times with different keys

AES (Advanced Encryption Standard)

  • Symmetric block cipher (also known as Rijndael)
  • 128-bit block size
  • Stronger key sizes: 128, 192, or 256 bits

RSA (Rivest–Shamir–Adleman)

  • Asymmetric encryption algorithm
  • Public key used for encryption, private key for decryption
  • Widely used for secure data transmission and key exchange

Other Concepts

  • Diffie-Hellman Key Exchange: Secure method for exchanging cryptographic keys over an insecure channel
  • Digital Signature: Verifies the authenticity and integrity of digital data
  • Digital Certificate: Contains public key and identity information, issued by a trusted Certificate Authority (CA)
  • SSL/TLS Handshake Protocol: Establishes a secure connection between client and server, involving cipher suite negotiation, key exchange, and identity verification using digital certificates.